WHEELS AND TYRES
The way most riders have their wheels are a strong and heavy back wheel and a light front wheel. It is important to have a strong back wheel as you spend a lot of time on it, and when you start to do drops of more than 6ft, it can bend.
The light front wheel keeps overall weight down, and makes the front end easy to pick up. Also strength is not so important on the front.
Tyres are more of personal preference, but most riders go for a fat back tyre, say 2.3", and a smaller front tyre, around 2.1", to keep front end weight down.
Overall you want to be strong and fat on the back, and small and light on the front.